The invention relates to a method and apparatus for cleaning inkjet cartridges in particular using pulsed laser irradiation.
It is a conventional technique in manufacturing inkjet cartridges to drill tiny inkjet nozzles (for example, diameter around 40 xcexcm for 2400 dpi inkjet printers) on the polyimide-based flexible circuit by ultra-violet (UV) laser ablation. During the laser drilling, polyimide debris generated will be distributed between the top transparent layer and polyimide substrate. It results in the deposition of black contamination materials around and inside the tiny inkjet nozzles. The contamination affects printing quality subsequently due to improper ink accuracy and poor flexible circuit contact with other device components. Accordingly an important issue in manufacturing the cartridges is to enhance the printer performance by removing surface contamination before the cartridge assembly. As printer technology develops, the tiny inkjet nozzles become smaller and smaller This makes the contamination removal even more critical. There are two available methods to remove the contamination: chemical solution cleaning, and plasma etching.
In the case of chemical solution cleaning, the flexible circuit is put into an appropriate cleaning chemical solution for a certain period of time until the contamination is completely etched away. The flexible circuit is then rinsed by de-ionized (DI) water and dried in a subsequence process.
This gives rise to certain problems. High cost and subsequent drying of the flexible circuit are the main drawbacks of this technology. When the chemical solutions etch away the contamination, a chemical reaction with the polyimide substrate materials can also take place, damaging the substrate. The chemical solution can also be corrosive to the thin conductive circuit on the polyimide substrate. Meanwhile, the flexible circuit has to be dried in the subsequent process after the cleaning, which increases the production cost and processing time, introducing a lower yield. Furthermore, maintenance and disposal of the chemical solutions increase the manufacturing cost as a result of environment protection overheads.
In the plasma etching approach, the flexible circuit is put inside a vacuum chamber and then irradiated by a plasma generated from a plasma source. Surface contamination is then removed due to the plasma interaction with the contamination materials. Contamination debris generated during the plasma etching can be taken away by a gas stream or with a sucker system. This technique also has several problems. The processing needs sophisticated equipment to provide a stable plasma source. In addition, it must be carried out in a vacuum, which increases the cost and manufacturing time. Plasma can etch away not only the contamination but also the polyimide substrate. Furthermore, the thin conductive circuit may be damaged inside the plasma atmosphere.
Though the two methods mentioned above have cleaning effects on the surface contamination, the associated disadvantages significantly affect the productivity of the contamination removal and the reliability of the flexible circuit in manufacturing and increase environment protection overheads.
It is an object of the invention to overcome or mitigate at least some of the above problems. According to the invention there is provided an inkjet circuit cleaning apparatus comprising a circuit holder, a laser for generating a laser beam and an optics subsystem arranged to focus the laser beam onto a circuit surface at the circuit holder.
The optics subsystem preferably includes a beam splitter for splitting off a portion of the beam to regulate the laser beam power The optics subsystem preferably includes a lens system made of two cylinder lenses for changing a circular laser beam into a narrow and long laser beam, which adjusts the laser beam size, shape and fluence on the flexible circuit.
The optics subsystem preferably includes a galvanometer arranged to scan the laser beam across a circuit surface.
The apparatus preferably further includes a diagnostic subsystem comprising a sensor arranged to sense whether the circuit surface has been cleaned, and preferably the sensor comprises one or more of an acoustic sensor, a plasma signal sensor or a surface pattern inspection monitor. The apparatus preferably further includes an apparatus controller arranged to receive a signal from the sensor and control the cleaning operation accordingly.
The laser preferably has a pulse duration of nanoseconds and a wavelength selected from the visible to the infrared range. For example the laser may be a YAG laser with a wavelength 1064 nm or 532 nm.
The laser beam more preferably has as at least one of the following characteristics: pulse duration 7 nano-seconds; wavelength 532 nm; fluence of 50 mJ/cm2; pulse number of 10.
Preferably the circuit holder is arranged to replace a cleaned circuit by a contaminated circuit.
The apparatus preferably further includes a contaminant removal mechanism, and preferably the contaminant removal mechanism comprises one of a vacuum source or a gas stream source, and the apparatus preferably further comprises a transparent protective cover between the circuit holder and the optics system to trap escaped contaminant.
Preferably the circuit comprises a flexible circuit for an inkjet printer cartridge. According to the invention there is further provided a method of cleaning an inkjet circuit comprising the steps of retaining a circuit to be cleaned in a circuit holder, generating a laser beam from a laser, and focusing and scanning the laser beam on the circuit surface via an optics subsystem.
The method preferably further comprises the steps of detecting when a portion of the circuit surface is cleaned and controlling the galvanometer to scan the beam across a non-cleaned portion of the surface.
The method preferably further comprises the step of detecting when a circuit is fully cleaned, and controlling the circuit holder to replace the circuit with a non-cleaned circuit.
The method is preferably for cleaning a flexible circuit of an inkjet printer cartridge.
As a result a dry process is available, in air, which does not need the sophisticated equipment and subsequent rinsing and drying process. There are also no chemical solutions involved. By proper control of the processing parameters, the laser irradiation can remove the contamination completely without any damage on the polyimide substrate and the thin conductive circuit. This invention can accordingly offer high productivity and low cost.
In the preferred embodiment appropriate processing parameters such as light wavelength, laser pulse duration, laser fluence and pulse number are selected for removal of the contamination. The contamination area on the polyimide substrate is selectively irradiated by the pulsed laser with the proper processing parameters. When the laser energy is absorbed, its photon energy can easily break the loose chemical bonds of the contamination. It induces a photo-ablation effect with the weak and localised plasma generation. At the same time, the fast momentum transferring from the laser beam to the polyimide substrate induces the rapid vibration of the substrate surface. It results in the contamination debris ejecting out of the irradiated surface at a high speed. With a gas stream or sucker system, the contamination debris can be easily taken away. In this process, laser fluence can be a critical parameter. With the applied suitable laser fluence, the laser irradiation can remove the contamination completely without any damage on the polyimide substrate. Furthermore, the laser irradiation is limited to around the tiny inkjet nozzle area. There is no laser interaction with the thin conductive circuit
Therefore, the chemical solution cleaning and plasma etching methods can be replaced by this technology. By using a suitable laser source and proper design of the laser processing parameters, it can achieve the goal of complete removal of the contamination without causing any damage on the polyimide substrate and the thin conductive circuit. Since it is a dry process, the disadvantages of high cost, low yield and chemical disposal can also be avoided.